Why does 2006 ford e-350 air conditioning blow hot air at idle?

Answer 1

Most cars require the air conditioner compressor to be turning at a decent rate to work effectively. Some cars will either slow down the compressor or completely stop turning when idle, depending on the system that keeps the belt moving. Also, the air requires a little time to cool and having the fan on high when the air conditioning is first turned on will cause it to blow warm air. Air needs time to "condition" with the gas to become cool and having the fan setting at the lowest speed will deliver the coolest air.

Alternatively, your compressor unit might be faulty or the belt that turns the unit may be slipping or broken (if it is uses a separate belt).